The number of adults living with dementia worldwide is expected to nearly triple, from an estimated 57 million in 2019 to 153 million in 2050, according to a study.

Researchers suggest this is due to population growth and population ageing.

They looked at four risk factors for dementia - smoking, obesity, high blood sugar, and low education - and the impact they will have on future trends.

For example, improvements in global education access are projected to reduce global dementia prevalence by 6.2 million cases by 2050.

But this will be countered by anticipated trends in obesity, high blood sugar, and smoking, which are expected to result in an additional 6.8 million dementia cases.

Dementia cases will rise in every country, with the smallest estimated increases in high-income Asia Pacific (53%) and western Europe (74%), the study suggests.

According to the estimates, the largest growth will be in north Africa and the Middle East (367%) and eastern sub-Saharan Africa (357%).

In the UK, the number of dementia cases is projected to increase by 75%, from just over 907,000 in 2019 to almost 1.6 million in 2050.

In western Europe, the number of dementia cases is expected to rise by 74%, from almost eight million in 2019 to nearly 14 million in 2050.

Relatively small increases in cases are expected in Greece (45%), Italy (56%), Finland (58%), Sweden (62%), and Germany (65%).

The Global Burden of Disease study is the first to provide forecasting estimates for adults aged 40 and older across 204 countries worldwide, and is published in The Lancet Public Health.

The experts project that improved access to education could lead to six million fewer cases of dementia worldwide by 2050.

But they also caution that this decrease would be offset by a projected seven million additional dementia cases linked to obesity, high blood sugar, and smoking.

The scientists call for more aggressive prevention efforts to reduce dementia risk through lifestyle factors, such as education, diet, and exercise.

Lead author Emma Nichols, from the Institute for Health Metrics and Evaluation (IHME) at the University of Washington, America, said: "Our study offers improved forecasts for dementia on a global scale as well as the country level, giving policymakers and public health experts new insights to understand the drivers of these increases, based on the best available data."

She added: "At the same time, we need to focus more on prevention and control of risk factors before they result in dementia.

"Even modest advances in preventing dementia or delaying its progression would pay remarkable dividends.

"To have the greatest impact, we need to reduce exposure to the leading risk factors in each country.

"For most, this means scaling up locally appropriate, low-cost programmes that support healthier diets, more exercise, quitting smoking, and better access to education.

"And it also means continuing to invest in research to identify effective treatments to stop, slow, or prevent dementia."

Across the world, more women are affected by dementia than men.

In 2019, women with dementia outnumbered men with dementia 100 to 69, and this pattern is expected to remain in 2050.

Co-author Dr Jaimie Steinmetz, from the IHME, said: "It's not just because women tend to live longer.

"There is evidence of sex differences in the biological mechanisms that underlie dementia.

"It's been suggested that Alzheimer's disease may spread differently in the brains of women than in men, and several genetic risk factors seem related to the disease risk by sex."

The authors acknowledge that their analysis was limited by a lack of high-quality data in several parts of the world, and by studies using different methodologies and definitions of dementia.